Porphyromonas (Bacteroides) gingivalis is a gram-negative anaerobic rod that is associated with chronic adult periodontal diseases. The mechanisms by which putative periodontopathogenic bacteria cause disease remains to be elucidated. Previous in vitro studies from various labs have suggested that human peripheral blood lymphocytes (PBL) respond to P. gingivalis by increased DNA synthesis, proliferation and production of lymphokines and/or antibodies. However, little is known of the cellular events that occur following in vitro stimulation with bacterium such as P. gingivalis and prior to DNA synthesis, proliferation and lymphokine production. Transmembrane signaling events have been extensively studied in lymphocytes following stimulation with monoclonal antibody for various T cell surface antigens (CD2, CD3, CD4, CD28, CD45) or with a T cell mitogen, phytohemagglutinin (PHA), and the resultant effector function(s), such as IL-2 production, determined. In order to have a better understanding of the mechanisms by which the host responds to P. gingivalis, it is proposed to stimulate normal human peripheral blood lymphocytes (PBL) with anti-CD3 to induce changes in cytosolic calcium, inositol phosphates and diacylglycerol. Once these assays are functional in our lab, it will be possible to determine the effect of P. gingivalis on cytosolic calcium, inositol phosphates and diacylglycerol levels in human PBL. We will also assay for in vitro proliferative responses to P. gingivalis, changes in lymphocyte surface antigens following incubation with this bacterium and lymphokine production. The cellular signalling events (Ca++, IP3) will be correlated with changes ill phenotype, proliferation and IL-2 production. These studies will provide information on the mechanisms by which host lymphocytes respond to P. gingivalis.